iPhone 8 Camera and the flash stops working after some usage.

So i replaced rear case (housing), display and rear camera on a iPhone 8 for a customer.

The phone worked great for a couple of days, the problem now is that the camera stops working together with the flash. This was a problem she was experiencing before my repair though. Anyways, i ordered the sidebutton flex and a new camera once again, but when she got in with the phone for repair the camera and flash was suddenly working again after i had unplugged the battery and then connected it back together. so she went home with her device but came back once again with same problem, so this time i actually swapped out the camera unit again and the camera works great.

Today i got a call from the same person and the issue persists, i feel like this problem is very odd but i would want to hear from anyone if they had the same problem or if someone knows a fix for this.

Thanks.